IIN Frontiers in Nanotechnology Seminar Series – Bo Brummerstedt Iversen
Professor Bo Brummerstedt Iversen
Professor, dr. scient. et. techn.
Center for Materials Crystallography
Department of Chemistry and iNANO
The figure of merit, zT = TS2σ/κ, has a central standing in thermoelectrics, and the individual components
(thermopower S, electrical conductivity σ, thermal conductivity κ) relate to the transport properties of the
thermoelectric material. Thus, the major part of thermoelectric science has focus on measuring and
interpreting transport properties. However, all understanding of physical or chemical properties of molecular
scale systems relies of precise knowledge of the atomic structure. Without knowledge of the composition
and three dimensional disposition of the atoms in space, rigorous interpretation of properties is impossible.
Structural techniques therefore must have a central standing in thermoelectrics.
In this talk I will discuss accurate crystal structures of high performance thermoelectric materials. The PbX
and SnX (X = S, Se, Te) systems have received immense interest due to record breaking figures of merit [1‐4]. In these materials the electrical properties originate from extraordinary electronic band structures, whereas the unexpected low thermal conductivity appears to have contributions from disorder and/or strong
anharmonic motion. The crystal structures have been analyzed with the nuclear enhanced maximum entropy
method (NXMEM) [5, 6]. Furthermore, a significant advance in nanoscale structure has been achieved in the
form of total scattering studies of thermoelectric thin films in the Fe‐Sb and Zn‐Sb systems [7, 8].
 Heremans et al, Science 2008, 321, 554
 Bozin et al., Science 2010., 330, 1660‐1663
 Pei et al., Nature 2011, 473, 66
 Biswas et al., Nature 2012, 489, 414
 Kastbjerg et al., Adv. Func. Mat. 2013, 23, 5477‐5483
 Christensen et al, Acta Crystallogr. Sect. A 2015, 71, 9–19
 Bauers et al, J. Am. Chem. Soc. 2015, in press
 Jensen et al., IUCr‐J 2015, in press.